226 BELL S YSTEM TECH NIC A L JOURNA L 



quency in its band. An A.V.C. circuit maintains the output power at 

 six db above one milliwatt. 



Fill. 4 — The assembled phase and transmission measuring system. 



Slave Oscillator 



To make possible the operation of the measuring attenuator, phase-shifter, 

 and phase and transmission difference detectors at constant frequency, the 

 inputs to the "S" and "X" channel modulators from the master and slave 



